Closure devices for containers suitable for holding liquids are known in the art. Examples of these devices are disclosed in WO 2009 126 042 A1, an international patent application filed in the name of Gunnar Berg and issued in Europe under no. EP 2 265 152 B.
More in detail, Berg discloses a cup comprising a container and a valve designed to close the container. The valve comprises a main body, attached to the container, and a cut-off member attached to the main body, and external to the container. The cut-off member is defined by a flexible member, which may be deformed by a pressure of the user's lips. Upon such deformation, liquid is free to flow outside the container.
More in detail, the main body of the valve has an anchor portion for the shut-off member, which is located in a central area. Such anchor portion is defined by a flange which projects out of a surface of the main body and located, in operation, substantially within the cup. Furthermore, the flange has slots for the passage of liquid.
According to Berg's teachings, the flange mainly acts as a splash guard, i.e. damps any splashes of liquid from inside the container, caused by vigorous stirring thereof. Thus, any movement of the liquid will impact against the cut-off member with a weaker force, and will not be able to move it.
Further teachings relating to closure devices may be found in GB 2 461 005 B. This document, a patent issued to And Design Ltd. discloses differential pressure valves for closing containers. These valves are very similar in structure to the devices as disclosed by Berg but, unlike the latter, are opened by the user by exerting a suction on the edge of the container where the cut-off member of the valve sealingly rests.